This invention relates to antenna arrays, and more particularly to techniques for suppression of surface/traveling waves for antenna arrays of notch radiators.
Notch radiators are often used in two-dimensional antenna arrays because the sensor systems containing them require precise control over the antenna pattern, including wide bandwidth and the ability to scan the radiation over a wide range of angles. Typically, such an array is formed from xe2x80x9csticks,xe2x80x9d as illustrated in FIG. 1. Each stick 20, 22, . . . is a one-dimensional array composed of several adjacent notch radiators 30. The two-dimensional array is formed by aligning several sticks side by side such that an air channel or trough 24 separates each stick from the next. The portion of the trough farthest from the radiator tips may be occupied by a cross-polarization load 26 made of material that absorbs any radiation not captured by the radiator.
The outer surface of such an antenna array forms a complex, corrugated periodic structure that supports propagation of a variety of surface/traveling waves above it and within it. These waves interfere with the desired radiating wave needed for normal operation and can cause significant undesirable variations in the antenna patterns, including excessive radiation in unwanted directions and complete lack of radiation in desired directions. These pattern variations can degrade sensor system performance.
It has proven difficult to reduce undesirable contributions to the antenna pattern without also interfering with normal patterns and operation.
An antenna system is disclosed which includes an array of notch radiators, arranged in aligned rows on longitudinal axes to define a series of troughs between adjacent notch radiator rows within an aperture area, each notch radiator including a tip region. A plurality of surface/traveling wave suppressors fabricated of microwave energy absorbing material is disposed in the troughs, so that a longest suppressor dimension is transverse or nearly transverse to the array face and so that a suppressor surface is transverse or nearly transverse to the longitudinal axes.